Instability of Uniform Concentration Conditions in Suspensions under Shear

Starkey, T V; James, R. E.

doi:10.1038/178207a0

Cited by 13 publications

(6 citation statements)

References 2 publications

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“…It seems unlikely on more general rheological grounds discussed by Starkey (37,65,66). Our in vivo measurements support Taylor's extra vivum studies (37,64).…”

Section: Axial Stream Of Erythrocytes In Glass Tubes and Blood Vesselssupporting

confidence: 80%

The Robin Fåhræus Memorial Lecture1

Copley¹

1989

BIR

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“…It seems unlikely on more general rheological grounds discussed by Starkey (37,65,66). Our in vivo measurements support Taylor's extra vivum studies (37,64).…”

Section: Axial Stream Of Erythrocytes In Glass Tubes and Blood Vesselssupporting

confidence: 80%

The Robin Fåhræus Memorial Lecture1

Copley¹

1989

BIR

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“…The theory dealt with here was briefly outlined in earlier papers (Starkey 1955(Starkey , 1956. In accordance with the mechanism indicated there, suspended particles, although distributed randomly over the whole section of a tube on entry to it, would be expected as a result of the operation of the least action forces to move towards the axis as t !…”

Section: The Laminar Flow Of Suspensions In Tubes (Development Of Thmentioning

confidence: 77%

“…The characteristic 'flattened paraboliform' velocity profile (Vejlens 1938) observable in such flow can readily be associated with this concentration distribution, for the central flattened region of the profile defines the 'core' in those cases where the 'entrance effect' is negligible.…”

Section: Velocity Profile Phenomena In'suspensoid Sols Under Shearmentioning

confidence: 97%

“…Again, and remembering that the least action forces vary with particle size and shape characteristics (Starkey 1955(Starkey , 1956, the core formed by shearing a sol containing particles of various sizes and shapes (and similarly the thrombus formed in cases of high hyperconcentration), would be expected to exhibit a characteristic arrangement of the particles composing it. Thus, for a sol containing particles all of the same shape but of several different sizes, a section through the core (or through the thrombus), normal to the direction of flow, would be expected to display a concentric…”

Section: Shear Dependence Of Viscosity Of Suspensoid Solsmentioning

confidence: 99%

“…In earlier papers (Starkey 1955(Starkey , 1956) a flow mechanism was described in accordance with which these viscosity variations were explained in terms of changes occurring, with shear rate, in the positions of the particles in the veiocity field. It was pointed out that this mechanism would provide an explanation of non-Newtonian behaviour independent of any assumed attributes particular to individual suspensoid sols, and therefore, of general applicability.…”

Section: General Introductionmentioning

confidence: 98%

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Some Physics Demonstrations

Perkal'skis¹

1964

Sov. Phys. Usp.

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A theory relating to the viscous,flow of stable suspensoid sols, and briefly outlined in earlier papers is extended in the present work.It suggests (i) that concentration patterns are developed within suspensoid sols as a result of shearing, (ii) that these patterns arise through the operation of 'least action forces'. (The existence of such forces is required in order that the principle of least action shall be applicable to those changes in the configuration of the system of particles comprising the disperse phase of the sol which accompany shearing), (iii) that the velocity distribution pattern within such a sol is related in any given case to the concentration pattern, (iv) that the anomalous properties of suspensoid sols under shear arise in consequence of the development of these patterns, and (v) that changes in these properties are due to changes in the parameters dejning these patterns, and these, in turn lead to variations in the magnitudes of the least action forces with changes in the shearing conditions. It leads, in the case of flow through capillary tubes to the following conclusions:(1) Shear dependence of viscosity is a universal characteristic of such sols. (2) The overall mean sol concentration within a tube during.flow is always less than the concentration in the reservoir from which it is supplied.(3) The mean concentration over any cross section diminishes systematically along a tube from a maximum value equal to the reservoir concentration (near to the entrance) to a minimum value at points nearer to the exit. (4) The overall mean sol concentration varies with flow rate from a maximum value (equal to the reservoir concentration) at zero rate of flow to a minimum value (alwaysgreater than one half of the reservoir concentration) at the highest rate,for non-turbulent Pow. (5) The velocity profile, as defined by the ratio of mean to maximum streaming velocity, is also shear dependent, the ratio varying systematically between limits of one harf and one. (6) The ratios of mean to maximum velocity and of mean tube concentration to reservoir concentration are equal to one another .for sols showing no appreciable Brownian movement and flowing in very long tubes. (7) These velocity and concentration ratios can under the conditions mentioned in (6), be expressed as a simple function of the relative viscosity of the sol. (8) The axial sol concentration increases systematically along the tube from a minimum value (equal to the reservoir concentration), near the tube entrance, to a maximum value which may be many times as great at points nearer to the exit. (This hyperconcentration will under appropriate conditions lead to the formation of a thrombus.)Experiments designed for the investigation of the conclusions numbered (1)) (2), (4), (5) and (7) are also described. The results yielded by these experiments support the conclusions mentioned.

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Viscosity of suspensions of coal in mineral oil

Moreland¹

1963

Can J Chem Eng

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Viscosity data for slurries of five solid particle systems suspended in a mineral oil are presented for solid concentrations up to 50% by volume. At volume concentrations of less than 30% the results are well represented by the Einstein equation in its fluidity form, the constant varying with the system between 2.65 and 3.15, (as compared with 2.5 in the theoretical equation). At higher concentrations the slurries are non‐Newtonian, and no satisfactory correlation is available in this region, very little complete data for the high concentration region have been published. Slurry viscosities are greater for smaller particles, and are greater for irregular particles than for spherical particles. Slurry viscosities in regions of high concentration can be considerably reduced by careful selection of particle size distribution. Pressure gradients measured in an experimental pipeline carrying a suspension of coal in oil in laminar flow could not have been predicted using the viscosities determined in the laboratory.

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Instability of Uniform Concentration Conditions in Suspensions under Shear

Cited by 13 publications

References 2 publications

The Robin Fåhræus Memorial Lecture1

The Robin Fåhræus Memorial Lecture1

Some Physics Demonstrations

Viscosity of suspensions of coal in mineral oil

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